<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    // alert('请输入你的年龄')
    // let age = prompt('')
    // alert('请输入你的姓名')
    // let name = prompt('')
    // alert(`大家好，我叫${name}，今年${age}岁了`)

    // let number1 = prompt('请输入第一个数')
    // let number2 = prompt('请输入第二个数')
    // document.writeln(parseFloat(number1) + parseFloat(number2))
    console.log(NaN + 1);
  const  num = 10
   console.log( num + 11)
   console.log( num + '11')
   console.log( num +  +'11')
  </script>
</body>

</html>